Turbomachine for generating power having a temperature measurement device in a region of the rotor

ABSTRACT

A turbomachine having a rotor is provided, wherein the rotor comprises a central holding element and rotor elements which are arranged thereon, is intended to permit faster start-up without reducing the lifetime of the rotor, while permitting better predictions relating to the remaining lifetime of the rotor. To this end, a contact element is arranged in a region of the rotor between the holding element and the rotor element, wherein the contact element comprises a temperature measurement device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International ApplicationNo. PCT/EP2012/065098 filed Aug. 2, 2012, and claims the benefitthereof. The International Application claims the benefit of EuropeanApplication No. EP11179152 filed Aug. 29, 2011. All of the applicationsare incorporated by reference herein in their entirety

FIELD OF INVENTION

The invention relates to a turbomachine having a rotor, wherein therotor comprises a central retaining element and rotor elements arrangedthereon.

BACKGROUND OF INVENTION

A turbomachine is a fluid energy machine in which energy is transferredbetween fluid and machine in an open space by means of a flow accordingto the laws of fluid dynamics via kinetic energy. Energy is normallytransferred by means of rotor blades which are shaped such that the flowaround them produces a pressure difference between the front and backsides (wing profile). A turbomachine typically consists of a rotatingpart, the rotor, and a stationary part, the stator.

A gas turbine is a turbomachine in which a gas under pressure expands.It consists of a turbine or expander, a compressor connected upstreamthereof, and a combustor connected between the two. The workingprinciple is based on the cyclic process (Joule process): thiscompresses air by means of the blading of one or more compressor stages,then mixes this air with a gaseous or liquid fuel in the combustor andignites and combusts the mixture. In addition, the air is used forcooling, in particular of components subjected to high thermal stresses.

This produces a hot gas (a mixture of combustion gas and air) whichexpands in the subsequent turbine part, wherein thermal energy isconverted to mechanical energy and then drives the compressor. In ashaft engine, the remaining portion is used to drive a generator, apropeller or other rotating loads. In a jet engine, by contrast, thethermal energy accelerates the hot gas stream, producing thrust.

The rotor of a turbomachine, particularly in the case of gas turbines,is a component which is subjected to high thermal and mechanicalstresses. It conventionally consists of a central retaining element, ashaft or axle, to which are attached the remaining rotating elementssuch as disks and rotor blades. In particular in the case of a coldstart of the turbomachine, the rotor disks are in this case subjected tovery high stresses. On one hand, the rotors experience considerableheating in the region of the blade roots, and on the other hand coolingair flows through the rotor so that the temperature of the material doesnot exceed the strength limits.

The flow structures and heat transfer effects which appear inside therotor are extremely complex and have for decades been the subject ofuniversity research the world over. This applies first and foremost tothe transient processes when starting up or shutting down the machines.

In practice, the temperatures occurring in the rotor—and in particularthe temperature gradients which give rise to thermal stresses—arecurrently estimated conservatively, i.e. on the safe side. This ofteninvolves FEM (finite element method), a numerical method for solvingpartial differential equations, with which solid-body simulations can becarried out. In this case, the boundary conditions are determined usingindividual prototype measurements. Sample measurements of thetemperature of individual rotor components are also carried out here inpart.

The data obtained in this manner are used, on one hand, to estimate themaximum number of start cycles that a rotor can withstand before it hasto be replaced and, on the other hand, to estimate a rotor preheat time,which is necessary in certain cases in order to reduce thermal stressesto an acceptable level and to keep the number of permitted start cycleshigh enough. However, waiting a certain time before commencement ofoperation of the rotor always implies increased energy consumption and alonger startup time for the turbomachine, which is undesirable,particularly for example in the case of gas turbine and steam turbinepower plants, as these often have to cover peak power requirements ofthe electrical grid at short notice.

SUMMARY OF INVENTION

It is therefore an object of the invention to indicate a turbomachinewhich allows faster startup without this reducing the lifespan of therotor, and at the same time allows better prediction of the remaininglifespan of the rotor.

This object is achieved, according to the invention, by a contactelement being arranged in a region of the rotor between the retainingelement and the rotor element, wherein the contact element comprises atemperature measurement device.

The invention thus proceeds from the consideration that faster startupand better estimation of the lifespan would be possible in particular ifespecially precise and up-to-date data on the temperature behavior ofthe rotor of a turbomachine for generating power were made available. Tothat end, it is possible, for example based on the adaptation totransient temperature profiles from FEM models, to derive analyticaltemperature formulae by means of which the material temperature can beestimated on the basis of measured operational data. An estimation ofthis kind must, however, always be conservative with respect tooperational safety and lifespan. This can for example have theconsequence that, during startup, there is an unnecessarily long waitfor the corresponding temperature conditions or even that the process ofstarting the turbomachine is locked, even though the required materialtemperature has been reached, as the temperature formula has estimatedthe temperature as too low.

For this reason, the temperature must be determined still moreprecisely. This can be achieved by directly measuring the temperature inthat region of the rotor which is of interest. This is howeverproblematic in that certain regions of the rotor, in particular the diskhubs subjected to particularly high thermal stresses, are arrangedinside the turbomachine and access to these is therefore difficult.Hence, a means should be found to measure the material temperature usingan appropriate arrangement of a temperature measurement device. This canbe achieved by the temperature measurement device being arranged in acontact element between the rotor element to be measured and theretaining element of the rotor. This can be effected with the aid oftemperature converters such as resistance sensors or thermocouples. Thecontact element is then pressed against the retaining element bycentrifugal force during rotation of the rotor, thus ensuring goodcontact and good heat transfer.

In this case the central rotor element is a tie rod and/or the rotorelement is a rotor disk, i.e. the contact element is located between thetie rod and the rotor disks attached thereto. Contact elements can thusbe attached to all disks over the entire axial length and thetemperature of these can thus be detected. At the same time, this meansthat the rotor of a stationary turbomachine designed for industrialpower generation is particularly stable and of simple construction.

Advantageously, said region of the rotor is the region which issubjected to the highest thermal loads in comparison to other regions.Indeed, not all regions of the rotor of the turbomachine are subjectedto the same level of load in operation. Thus, for example, the disk hubsof the rotor are comparatively highly loaded parts. In order that atemperature measurement does not need to be carried out in all regions,it should be ensured that in every case the highly loaded regions whichare critical for calculating the lifespan are precisely measured.

Thus, determining the lifespan of the rotor is improved while reducingexpenditure.

In a further advantageous configuration, the contact element is mountedrotatably on an axle, wherein the axle is attached to the centralretaining element. This means that the contact element is configured asa pawl which is attached to the central retaining element, in particularthe tie rod. By virtue of the rotatably mounted axle, this pawl moves,under the effect of centrifugal force, outward on the side facing awayfrom the axle and wedges the surrounding rotor component, in particularthe rotor disk. The pawl thus serves two purposes: on one hand to attachand centrally and symmetrically secure the rotor disk, and on the otherhand in the chain of transmitting the signal of the disk temperature tothe pawl temperature, data transmission and monitoring. The pawls mayalso be used to damp oscillations in the rotor. An advantageousembodiment of the pawl is in this case such that even at turningrotational speed, i.e. when the turbomachine is started up, it bearsagainst the disk with sufficient force and such that at operating speedit allows a relative expansion of the rotor components.

The contact element advantageously comprises a thermally conductivematerial on its side facing the rotor element. This ensures aparticularly good transfer of heat from the region to be measured on therotor disk to the temperature measurement device, which improves thequality of the temperature determination.

In a further advantageous configuration, the contact element comprisesan insulating material on its side facing the central retaining element.This prevents an input of heat or a loss of heat in the direction of thecentral tie rod. This also improves the quality of the temperaturedetermination.

The central retaining element advantageously comprises, in the region ofa bearing assigned to it, a transmitter connected to the temperaturemeasurement device on the data side and serving to transmit thetemperature data. The data line from the temperature measurement devicethus runs on or in the central retaining element, e.g. the tie rod tothe bearing, which is typically arranged in an outer region. Thetransmitter can for example be designed according to the inductiveprinciple or by means of sliding contacts and thus allows signals to betransmitted to the stationary components. An embodiment of this type canbe operationally active for long periods of operation. For reasons ofgood accessibility, positioning the transmitter on a bearing also makesit possible to carry out maintenance without dismantling the rotor.

In an advantageous configuration, a plurality of contact elements isarranged symmetrically about the central retaining element. This avoidsimbalances and allows temperature measurement over the entirecircumference.

The turbomachine is advantageously a gas turbine. Specifically in gasturbines, whose components, in particular the rotor, are subjected tothe highest thermal and mechanical stresses, the described configurationis of considerable advantage with respect to determining lifespan andreduces the startup time without sacrificing operational safety orlifespan.

A turbomachine of this type is advantageously used in a power plant.

The advantages achieved with the invention are in particular that, byvirtue of measuring over the entire lifespan of the turbomachine,up-to-date data on the temperature behavior of the rotor are available.With the aid of these data, substantially more precise lifespanestimates for rotors can be made, and the number of permissible starts,corresponding to physical actualities, can be adapted in an up-to-datemanner. This is an immediate industrial advantage for the operator, inparticular in the case of installations with frequent cold starts. Atthe same time, continuous temperature measurement permits a betterestimation of the rotor lifespan and a shortening of the startup processwithout reducing the lifespan. In addition to the time saving and thusincreased flexibility, less energy is also used for startup. Directtemperature measurement, together with the signal line in the region ofthe bearings, further presents a particularly maintenance-friendlysystem for continuous temperature measurement.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail with reference to a drawing,in which:

FIG. 1 shows an axial section through a gas turbine,

FIG. 2 shows an axial section through a partial region of the rotor ofthe gas turbine of FIG. 1, and

FIG. 3 shows a radial section through a contact element of the gasturbine.

DETAILED DESCRIPTION OF INVENTION

In all figures, identical parts are given the same reference signs.

A gas turbine 101 as shown in FIG. 1 is a turbomachine. It has acompressor 102 for combustion air, a combustor 104 and a turbine unit106 for driving the compressor 102 and a generator (not shown) or a workmachine. To that end, the turbine unit 106 and the compressor 102 arearranged on a common turbine shaft 108, also termed the turbine rotor,to which the generator or, as the case may be, the work machine is alsoconnected, and which is mounted rotatably about its central axis 109.These units form the rotor of the gas turbine 101. The combustor 104,which is embodied as an annular combustor, is equipped with a number ofburners 110 for burning a liquid or gaseous fuel.

The turbine unit 106 has a number of rotary rotor blades 112 which areconnected to the turbine shaft 108. The rotor blades 112 are arranged ina ring shape on the turbine shaft 108 and thus form a number of rotorblade rings or rows. The turbine unit 106 further comprises a number ofstationary guide vanes 114 which are attached, also in a ring shape, toa guide vane carrier 116 of the turbine unit 106 so as to form guidevane rows. The rotor blades 112 serve in this context to drive theturbine shaft 108 by impulse transfer from the working medium M whichflows through the turbine unit 106. The guide vanes 114 serve, on theother hand, to guide the flow of the working medium M between in eachcase two successive—as seen in the direction of flow of the workingmedium M—rotor blade rows or rotor blade rings. A successive pair,having a ring of guide vanes 114 or a guide vane row and of a ring ofrotor blades 112 or a rotor blade row, is in this context also termed aturbine stage.

Each guide vane 114 has a platform 118 which is arranged as a wallelement for fixing the respective guide vane 114 to a guide vane carrier116 of the turbine unit 106. The platform 118 is in this context acomponent which is subjected to comparatively high thermal loads andwhich forms the outer limit of a hot gas channel for the working mediumM which flows through the turbine unit 106. Each rotor blade 112 is, inanalogous fashion, attached to the turbine shaft 108 by means of aplatform 119, also termed the blade root.

A ring segment 121 is in each case arranged on a guide vane carrier 116of the turbine unit 106 between the spaced apart platforms 118 of theguide vanes 114 of two adjacent guide vane rows. The outer surface ofeach ring segment 121 is in this context also exposed to the hot workingmedium M flowing through the turbine unit 106, and is separated in theradial direction from the outer end of the rotor blades 112 locatedopposite by a gap. The ring segments 121 arranged between adjacent guidevane rows serve in this context in particular as covering elements whichprotect the interior housing in the guide vane carrier 116, or otherintegrated housing parts, from thermal overloading caused by the hotworking medium M which is flowing through the turbine 106.

In an exemplary embodiment, the combustor 104 is configured as what istermed an annular combustor, wherein a multiplicity of burners 110,arranged around the turbine shaft 108 in the circumferential direction,open into a common combustor space. To that end, the combustor 104 isconfigured in its entirety as an annular structure which is positionedaround the turbine shaft 108.

In order to permit a better prediction of the lifespan of the rotor andthe requisite possible preheat times, the gas turbine 101 is configuredfor a temperature measurement in the rotor. This is shown in FIG. 2,which represents an enlarged section through the rotor of the gasturbine 101.

This shows the more detailed construction of the rotor in axial section:the already-described rotor blades 112 of the turbine unit 106 are ineach case attached, together with the platforms 119, to one rotor disk122 per rotor blade row. The rotor disks 122 are attached to a tie rod124. A pawl 126, which is rotatably attached to an axle 128 by means ofnuts 130, is arranged in the region subjected to the greatest thermalload. A data line 132 leads to a temperature measurement device 134 inthe pawl 126.

FIG. 3 shows a radial section through the rotor, wherein the shape ofthe pawl 126 can be seen. The temperature measurement device 134 isarranged in the region facing the rotor disk 122. A material with goodthermal conductivity is applied on top of it and an insulator underneathit. The data line 132 leads from the temperature measurement device 134to a bearing (not shown) of the rotor, where it leads into a transmitterwhich transmits the temperature data to stationary components.

When the tie rod 124 rotates with the rotor, the pawl 126 is pressedagainst the rotor disk 122 such that there exists a good transfer ofheat to the temperature measurement device 134. The pawl 126 thusfulfills multiple functions: on one hand it secures the rotor disk andprovides radial equalization, on the other hand it serves as atransmission member in the temperature measurement. In addition, thepawl 126 serves to damp oscillations.

By means of the temperature measurement, the startup time of the gasturbine 101 is on one hand reduced. On the other hand, temperature datafor the rotor are available, which permits particularly precisepredictions with respect to the lifespan of the gas turbine 101.

1. A turbomachine for generating power, comprising: a rotor, wherein therotor comprises a central retaining element in the form of a tie rod androtor elements in the form of rotor disks arranged thereon, wherein acontact element is arranged in a region of the rotor between the centralretaining element and the rotor element, wherein the contact elementcomprises a temperature measurement device.
 2. The turbomachine asclaimed in claim 1, wherein said region of the rotor is the region whichis subjected to the highest thermal loads in comparison to otherregions.
 3. The turbomachine as claimed in claim 1, wherein the contactelement is mounted rotatably on an axle, wherein the axle is attached tothe central retaining element.
 4. The turbomachine as claimed in claim1, wherein the contact element comprises a thermally conductive materialon its side facing the rotor element.
 5. The turbomachine as claimed inclaim 1, wherein the contact element comprises an insulating material onits side facing the central retaining element.
 6. The turbomachine asclaimed in claim 1, wherein in the region of a bearing assigned to thecentral retaining element, the central retaining element comprises atransmitter connected to the temperature measurement device on a dataside of the device, wherein said transmitter transmits temperature data.7. The turbomachine as claimed in claim 1, wherein a plurality ofcontact elements is arranged symmetrically about the central retainingelement.
 8. The turbomachine as claimed in claim 1, wherein saidturbomachine is configured as a gas turbine.
 9. A power plant comprisinga turbomachine as claimed in claim 1.